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acidification of a mixture of solutions that contain GeO 3 2 - and MoO 4 2 - . The second acidification was carried out to prevent the formation of persistent IA Astrafloxin with isopolymolybdate ions. The excess of molybdate ions was masked with hydroxy acids. The reaction of the formation of IA MGK with astrafloxin occurs instantly . The reaction is selective with a fairly high sensitivity. The selectivity of the formation reaction may be impaired by the formation of colored IAs with large anions, but their solubility is much greater than the solubility of IAs with heteropolyanions. Therefore, there is no interfering �H�I�I�H�F�W��R�I��V�X�F�K��D�Q�L�R�Q�V��GKH 3 - , SO 4 2 - , NO 3 - . Table 2 shows data on the effect of a number of ions on the determination of germinate ions. Table 2. The maximum excess of foreign ions that does not affect the determination of Ge ((IV) in the form of �*�HFh 12 H 40 4 - �Z�L�W�K��$�)��K��*�H�� �

�� - 7 mol/L. interfering ion Na + , K + , Mg 2+ NO 3 - , Cl - , AsO 4 3 - Ni 2+ , Zn 2+ , Cu 2+ Fe 3+ CO 3 2 - , PO 4 3 - SiO 3 2 - molar ratio K Ge ��K X 1:1000 1:500 1:400 1:100 1:50 1:5 The decrease in the interfering effect of silicates in the determination of germanate ions is explained by the fact that the reaction for the formation of MGC proceeds in a more acidic environment. In this pH range, molybdosilicate is not fully formed. In this case, the molybdosilicate complex (MSC) is formed very slowly for 15 - 20 minutes, and the modibdogermanate complex – quickly, 1 - 2 minutes. We have for the first time shown the possibility of a highly sensitive visual test determination of Ge (IV) after selective concentration of IA 12 - MGA with polymethine dye AF. Calibration graphs were obtained for the colorimetric determination of Ge (IV) in the coordinates of the R and B functions (red and blue) – logC (Tab le 3) or (255 - G) 2 / 2G = f (C) and the possibility of correlation of this dependences with spectrophotometric in coordinates A - (255 - G) 2 / 2G. Table 3. Color coordinates R, G, B obtained after scanning stained samples of filter paper with sorbed IA GeMo 12 O 40 4 - - AF C Ge � 10 - 6 , mol/L R Color G Color B Color l g(C) blank test 243 242 241 0 0,04 230 196 186 - 7,398 0,2 188 177 127 - 6,699 0,4 154 169 99 - 6,398 0,6 135 134 68 - 6,222 0,8 127 87 39 - 6,097 1 113 79 24 - 6,00 2 92 44 12 - 5,699 The dependence of the R, G, and B color coordinates on the concentration of IA is exponential (Fig. 3 .a, Fig. 3 .b). R and G color coordinates upon IA GeMo 12 O 40 4 - - AF sorption change most naturally and in a wider interval. Data were processed using the modif ied Kubelka - Munk equation (Fig. 4 ). The equation of the calibration graph in coordinates (255 - G) 2 / 2G = f (C), where G is the value of the color coordinate R, and C is the concentration of Ge (IV) in mol/L , is described by the expression ( - 4,1 �r 1,5) + (3,16 �r 0,11) �Â������Â� K��*�H���,�9����W�K�H��F�R�U�U�H�O�D�W�L�R�Q��F�R�H�I�I�L�F�L�H�Q�W� is 0.995. The detection limit calculated by the 3Sa / b formula is 4 �Â��� - 8 mol/L . Fig. 3 Z� Dependence of coordinates R - functions of Ge (IV) concentrat

ion after sorption GeMo 12 O 40 4 - - AF Fig. 3 .b. Dependence of coordinates B - functions of Ge (IV) concentration after sorption IA GeMo 12 O 40 4 - - AF . Calibration graphs were obtained for the colorimetric determination of Ge (IV) in the coordinates of the R and B functions (red and blue) – logC (Tab le 3) or (255 - G) 2 / 2G = f (C) and the possibility of correlation of this dependences with spectrophotomet ric in coordinates A - (255 - G) 2 / 2G. The need to analyze many different objects for the content of germanium requires the development of simple sensitive methods for a preliminary assessment of their content for the correct further selection of quantitat ive methods. The developed method for the determination of germanium in the form of AF - 12 - MGK IA was used and 0 0 , 5 1,0 2 60 80 100 120 140 160 180 200 R C Ge × 10 - 6 , mol/L 2 4 0 1,5 0 0,5 1 , 0 1 , 5 2 , 0 4 0 80 100 120 140 160 C Ge × 10 - 6 , mol/L ¦ 1 8 0 3 of the city of Kryvyi Rih and surrounding area s. The study was conducted on many parameters, inc luding the definition of Germanium . Germanium is a potentially dangerous element for human health [15]. However, the results of research over the last 5 years show that the content of German ium , even in ma n - mad e reservoirs, does not exceed 1 µg/ l. This is due to the rather low mobility o f inorganic compounds in Germanium . It also shows that there is no potential environmental threat from Germany in such an industrial region as the city of Kryvyi Rih. R eferences 1 . A.M. Garc �Õ“ a - Campaña, F. Alés Barrero, A. Lupiáñez González, M. Román Ceba. Analytica Chimica Acta. 1 - 2 (447), 219 – 228 (2001) . doi:10.1016/S0003 - 2670(01)01288 - 0. 2 . H. Matusiewicz , M. Krawczyk. Anal. Lett. 16 (46), 2543 (2010). doi:10.1080/00032711003725631 3. I.P. Alimarin , Zhurn. analit. himii 6(39), 965( 1984 ) 4 . A.B. Vishnikin , D iss ertation, Odessa , 2012 5 . L.I. Ganago , Zhu rn. analit. himii 26( 1 ), 104 – 109 (1971) 6 . E.N. Dorohova , Zhurn. analit. himii 8(50), 870 ( 1995 ) 7 . F.V. Mirzoyan , Zhurn. analit. himii 3(55), 289 ( 2000 ) 8 . F.V. Mirzoyan , Talanta. 27, 1050 (1980) 9 . L.V. Myishlyaeva , Nauka, 209 (1972) 10 . M. McMahon , F . Regan, H . Hughes , Food Chemistry 3(97), 411 (200 6 ) . doi:10.1016/j.foodchem.2005.05.018 1 1 . S.K. Tobia , M.F. El - Shahat , E.A. Saad , Microchemical Journal 23 (4 ) , 525 – 529 ( 1978 ) 1 2 . A . Harada , T . Tarutani , K . Yoshimura , Analytica Chimica Acta 209 , 333 – 338 ( 1988 ) 1 3 . V.M. Ivanov, O.V. Kuznetsova , Uspekhi khimii. 5 (70), 411 ( 2001 ) . doi:10.1070/RC2001v070n05ABEH000636 1 4. S.V. Himchenko , L.P. Eksperiandova , Tsvetometriya v instrumentalnom i vizuanom test analize ( K�K�U�R�P�D�W�L�F�L�W�\ in instrumental and visual test analysis) ( La mbert Academic Publishing, 2 014) 15. Shyy - Hwa Tao, P. M. Bolger , Regulatory Toxicology and Pharmacology 25 (3), 211 – 219 (1997). doi:10.1006/rtph.1997.1098 5 of the city of Kryvyi Rih and surrounding area s. The study was conducted on many parameters, inc luding the definition of Germanium . Germanium is a potentially dangerous element for human health [15]. However, the results of research over the last 5 years show that the content of German ium , even in ma n - mad e reservoirs, does not exceed 1 µg/ l. This is due to the rather low mobility o f inorganic compounds in Germanium . It also shows that there is no potential environmental threat from Germany in such an industrial region as the city of Kryvyi Rih. R eferences 1 . A.M. Garc &#

0;Õ“ a - Campaña, F. Alés Barrero, A. Lupiáñez González, M. Román Ceba. Analytica Chimica Acta. 1 - 2 (447), 219 – 228 (2001) . doi:10.1016/S0003 - 2670(01)01288 - 0. 2 . H. Matusiewicz , M. Krawczyk. Anal. Lett. 16 (46), 2543 (2010). doi:10.1080/00032711003725631 3. I.P. Alimarin , Zhurn. analit. himii 6(39), 965( 1984 ) 4 . A.B. Vishnikin , D iss ertation, Odessa , 2012 5 . L.I. Ganago , Zhu rn. analit. himii 26( 1 ), 104 – 109 (1971) 6 . E.N. Dorohova , Zhurn. analit. himii 8(50), 870 ( 1995 ) 7 . F.V. Mirzoyan , Zhurn. analit. himii 3(55), 289 ( 2000 ) 8 . F.V. Mirzoyan , Talanta. 27, 1050 (1980) 9 . L.V. Myishlyaeva , Nauka, 209 (1972) 10 . M. McMahon , F . Regan, H . Hughes , Food Chemistry 3(97), 411 (200 6 ) . doi:10.1016/j.foodchem.2005.05.018 1 1 . S.K. Tobia , M.F. El - Shahat , E.A. Saad , Microchemical Journal 23 (4 ) , 525 – 529 ( 1978 ) 1 2 . A . Harada , T . Tarutani , K . Yoshimura , Analytica Chimica Acta 209 , 333 – 338 ( 1988 ) 1 3 . V.M. Ivanov, O.V. Kuznetsova , Uspekhi khimii. 5 (70), 411 ( 2001 ) . doi:10.1070/RC2001v070n05ABEH000636 1 4. S.V. Himchenko , L.P. Eksperiandova , Tsvetometriya v instrumentalnom i vizuanom test analize ( K�K�U�R�P�D�W�L�F�L�W�\ in instrumental and visual test analysis) ( La mbert Academic Publishing, 2 014) 15. Shyy - Hwa Tao, P. M. Bolger , Regulatory Toxicology and Pharmacology 25 (3), 211 – 219 (1997). doi:10.1006/rtph.1997.1098 5 E3S Web of Conferences 166 , 01013 (2020) https://doi.org/10.1051/e3sconf/202016601013 ICSF 2020 acidification of a mixture of solutions that contain GeO 3 2 - and MoO 4 2 - . The second acidification was carried out to prevent the formation of persistent IA Astrafloxin with isopolymolybdate ions. The excess of molybdate ions was masked with hydroxy acids. The reaction of the formation of IA MGK with astrafloxin occurs instantly . The reaction is selective with a fairly high sensitivity. The selectivity of the formation reaction may be impaired by the formation of colored IAs with large anions, but their solubility is much greater than the solubility of IAs with heteropolyanions. Therefore, there is no interfering �H�I�I�H�F�W��R�I��V�X�F�K��D�Q�L�R�Q�V��GKH 3 - , SO 4 2 - , NO 3 - . Table 2 shows data on the effect of a number of ions on the determination of germinate ions. Table 2. The maximum excess of foreign ions that does not affect the determination of Ge ((IV) in the form of �*�HFh 12 H 40 4 - �Z�L�W�K��$�)��K��*�H�� �

�� - 7 mol/L. interfering ion Na + , K + , Mg 2+ NO 3 - , Cl - , AsO 4 3 - Ni 2+ , Zn 2+ , Cu 2+ Fe 3+ CO 3 2 - , PO 4 3 - SiO 3 2 - molar ratio K Ge ��K X 1:1000 1:500 1:400 1:100 1:50 1:5 The decrease in the interfering effect of silicates in the determination of germanate ions is explained by the fact that the reaction for the formation of MGC proceeds in a more acidic environment. In this pH range, molybdosilicate is not fully formed. In this case, the molybdosilicate complex (MSC) is formed very slowly for 15 - 20 minutes, and the modibdogermanate complex – quickly, 1 - 2 minutes. We have for the first time shown the possibility of a highly sensitive visual test determination of Ge (IV) after selective concentration of IA 12 - MGA with polymethine dye AF. Calibration graphs were obtained for the colorimetric determination of Ge (IV) in the coordinates of the R and B functions (red and bl

ue) – logC (Tab le 3) or (255 - G) 2 / 2G = f (C) and the possibility of correlation of this dependences with spectrophotometric in coordinates A - (255 - G) 2 / 2G. Table 3. Color coordinates R, G, B obtained after scanning stained samples of filter paper with sorbed IA GeMo 12 O 40 4 - - AF C Ge � 10 - 6 , mol/L R Color G Color B Color l g(C) blank test 243 242 241 0 0,04 230 196 186 - 7,398 0,2 188 177 127 - 6,699 0,4 154 169 99 - 6,398 0,6 135 134 68 - 6,222 0,8 127 87 39 - 6,097 1 113 79 24 - 6,00 2 92 44 12 - 5,699 The dependence of the R, G, and B color coordinates on the concentration of IA is exponential (Fig. 3 .a, Fig. 3 .b). R and G color coordinates upon IA GeMo 12 O 40 4 - - AF sorption change most naturally and in a wider interval. Data were processed using the modif ied Kubelka - Munk equation (Fig. 4 ). The equation of the calibration graph in coordinates (255 - G) 2 / 2G = f (C), where G is the value of the color coordinate R, and C is the concentration of Ge (IV) in mol/L , is described by the expression ( - 4,1 �r 1,5) + (3,16 �r 0,11) �Â������Â� K��*�H���,�9����W�K�H��F�R�U�U�H�O�D�W�L�R�Q��F�R�H�I�I�L�F�L�H�Q�W� is 0.995. The detection limit calculated by the 3Sa / b formula is 4 �Â��� - 8 mol/L . Fig. 3 Z� Dependence of coordinates R - functions of Ge (IV) concentration after sorption GeMo 12 O 40 4 - - AF Fig. 3 .b. Dependence of coordinates B - functions of Ge (IV) concentration after sorption IA GeMo 12 O 40 4 - - AF . Calibration graphs were obtained for the colorimetric determination of Ge (IV) in the coordinates of the R and B functions (red and blue) – logC (Tab le 3) or (255 - G) 2 / 2G = f (C) and the possibility of correlation of this dependences with spectrophotomet ric in coordinates A - (255 - G) 2 / 2G. The need to analyze many different objects for the content of germanium requires the development of simple sensitive methods for a preliminary assessment of their content for the correct further selection of quantitat ive methods. The developed method for the determination of germanium in the form of AF - 12 - MGK IA was used and 0 0 , 5 1,0 2 60 80 100 120 140 160 180 200 R C Ge × 10 - 6 , mol/L 2 4 0 1,5 0 0,5 1 , 0 1 , 5 2 , 0 4 0 80 100 120 140 160 C Ge × 10 - 6 , mol/L ¦ 1 8 0 3 E3S Web of Conferences 166 , 01013 (2020) https://doi.org/10.1051/e3sconf/202016601013 ICSF 2020 * Corresponding author: vitro090@gmail.com Visual test determination of trace amounts of germanium in the form of an ionic associate of 12 - molybdogermanate with astrafloxin Teti ana Selivanova 1 ,* , Andrey Vishnikin 2 , and Lyudmila Tsiganok 2 1 Kryvyi Rih State Pedagogical University, Kryvyi Rih, Ukraine 2 Oles Honchar Dnipro National University, Dnipro, Ukraine Abstract. Sorption - colorimetric and naked eye determination of germanium as ion associates of GeMo 12 O 40 4 – with triphenylmethane dyes is described . The sorption of the ionic associates (IA) of 12 - molybdogermanat with astrafloxin (AF) on filter paper was studied. The colored scales for naked eye detection and dependence of chromaticity coordinates from the germanium (IV) concentration were obta ined. The methods were applied to the determination of germanium (IV) in coked coal, iron ore, and in wate rs in the concentration range from 4•10 – 8 to 1•10 – 6 mol• L – 1 . The developed test - sys

tems for the determination of Germanium in natural and technological obje cts were tested in the course of training students of chemistry of Kryvyi Rih State Pedagogical University. I ntroduction Control of the content of germanium is necessary when it is extracted from ores, concentrates, coal, in its production, in cosmetics and medicines, in food. Plants that are capable of absorbing germanium and its compounds from the soil include: ginseng, garlic, camphor, aloe, tomatoes, beans , chickpeas , sunflower seeds , mushrooms and wheat bran . Germanium is also found in milk and in salmon meat . Germanium is an important trace element for humans, capable of accumulation. But its excess in the body or lack leads to the formation of various diseases. Germa n ium deficiency can be dangerous, since in this case the risk of the onset and development of cancer, as well as osteoporosis, is increased. Today it is necessary to have reliable, simple and relatively fast methods for its determination. The main methods for the determination of germanium (IV) today: atomic absorption method with electro - thermal atomization of the sample (AAS - ETA) [ 1 , 2 ], with mandatory preliminary concentration, atomic emission spectroscopy with inductively coupled plasma (AES - ICP ) [ 4 ], voltam per metric determination of germanium. Highly selective methods of atomic absorption analysis with electrothermal atomization or hydride version have their drawbacks. First of all, matrix elements interfere strongly with the determination, and the separation process only complicates and increases the analysis time. X - ray spectral and neutron activation methods to achieve sensitive, Sn = 10 – 3 �J�� But as for Germanium there is the problem of the formation of refractory carbides, introduced impurit ies from reagents, and other factors that interfere with the determination using physical methods of determination. A significant part of the existing methods for determining germanium (IV) are spectrophotometric, with mandatory separation procedures. The main methods of separation are distillation or extraction of germanium chloride in a strongly acidic medium in the f orm of a complex with phenylfluorone or other reagents. But these methods also have their drawbacks - the slow formation of a complex with phenylfluorone. Therefore, it is relevant to develop highly sensitive, express methods for the determination of low c ontents of germanium (IV) and the creation of test methods for its semiquantitative determination. To enhance the analyti cal signal in modern analysis, began to use the inclusion of chromophore groups with a high molar absorption coefficient in the analyti cal form. Until this time, triphenylmethane dyes, antipyrine and rhodamine dyes were most widely used (Table 1). The pH range in which these dyes exist in a cationic form is narrow. Recently, polymethine series dyes with a high molar absorption coefficient and a sufficiently wide pH range for the existence of singly charged cations have attracted their attention. With these dyes, ionic associates (IA) of heteropolyanions (HPA) form solutions or pseudocolloidal solutions that allow the determination of heter oatom elements at a concentration level of 10 – 8 – 10 – 7 mol/L [3, 6]. Currently, there are not enough test methods for determining germanium . This work is devoted to studying the conditions of selective sorption of the ionic associate (IA) of the molybdogermanium heteropolyanion (GPA) with the © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons At tribution License 4.0 (htt p ://creativecommons.or g /licenses/b y /4.0/). E3S Web of Conferences 166 , 01013 (2020) https://doi.org/10.1051/e3sconf/202016601013 ICSF 20